Purchase computer software that will allow you to make three-dimensional designs. You can complete the model only in the software or you can take the finished specifications to a printer to print out a physical model of the wrist when you are finished.
Use the design tools to create a line representing the two forearm bones, the ulna and the radius, connected to an axis joint, which will represent the wrist joint.
Design a hand that attaches to the other end of the joint. Make sure these components all connect to one another in a straight line.
Select the wrist joint and click on the "Modify" tool in the toolbox.
Select the "Axis" for the joint and create two of them. You can call the axis "Y" and "Z." This will be how the joint rotates.
Click on the "IK Handle" tab and assign the handle to both axis points. Once this is done, you will then have control of the wrist joint in the controls.